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Case Hardening

Case hardening is the carburising, hardening and tempering of components made of ferrous steel.

Case hardening is always used when a component with both a ductile centre and a hard surface is required.  To be able to achieve this requirement through heat treatment the surface layer of the material must have a carbon content of about 1 % with an internal carbon content of no more than 0.15 %

Case hardening is usually carried out at temperature between 880 to 980 °C.

The surface of the component is enriched with carbon through diffusion.  The usual range of case depths lies between 0.1 und 2.5 mm.

Following the carburising the carburised components are hardened and tempered.  Tempering is necessary to alleviate any stresses that have developed and to achieve the requisite final strength.

Hardening and tempering confer a high surface hardness and strength on the component.  The core, however, remains in a ductile, annealed condition

Case hardening is carried out in a gas flow or a salt-bath.  A salt-bath enables partial hardening without prior isolation of specific areas of the component.

 

Suitable Materials

Case hardened steels and construction steels with relatively low carbon content.

 

Advantages of Case hardening

  • Improved mechanical properties
  • Increased abrasion resistance through hard surface layer
  • High resilience
  • Ductile core increases flexuring strength
  • Preferential process for gear components
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